1. Field of the Invention
Embodiments of the present invention generally relate to methods and apparatuses for gripping and shearing a downhole cable.
2. Description of the Related Art
FIG. 1 is a longitudinal sectional view of a subterranean wellbore 5. After the wellbore 5 has been drilled through a hydrocarbon-bearing formation, i.e., crude oil and/or natural gas, the wellbore 5 may be completed by running in a string of casing 10 which may be cemented 40 in place. Thereafter, the casing 10 may be perforated 45 to permit the fluid hydrocarbons 2 to flow into the interior of the casing 10. The hydrocarbons 2 may be transported from the production zone of the wellbore 5 through a production tubing string 15 which is concentrically disposed relative to the casing. An annulus 35 defined between the casing 10 and the production tubing 15 may be isolated from the producing zone with a packer 30. One or more blowout preventers 25 may be provided in the wellhead 20 to shut-in the wellbore 5 in an emergency.
An instrumentation sub 50 may be assembled with the production tubing 15 and in data communication with the surface via a cable 55 extending to the surface along an outer surface of the production tubing 15. The instrumentation sub 50 may include pressure sensor, a temperature sensor, and/or a flow meter which provides useful data to the surface operator in producing the wellbore. The instrumentation sub 50 may be electrical or optical and the cable 55 may be correspondingly electrical or optical. Alternatively or additionally, a hydraulically operated valve (not shown) may be assembled with the production tubing and the cable may instead be or additionally include hydraulic tubing extending to the surface for control of the valve by the surface operator.
It may become desirable to cut the production tubing 15 at a predetermined depth in the wellbore, such as after depletion of the production zone or failure of downhole equipment. Typically a tubing cutter is lowered into the production tubing 15 until the tubing cutter reaches the predetermined depth. The tubing cutter may then be operated to cut or score the production tubing. However, the tubing cutter is unable to cut the cable 55. Once the production tubing is cut or scored, the production tubing may be placed in tension from the surface (thereby severing the production tubing at the score if it is not already cut). Since the cable 55 has not been cut, the cable may also be broken. However, it is unlikely that the cable 55 will break at or near the predetermined depth. If the cable breaks at a substantial length above the predetermined depth, then a nest of cable will remain once a portion of the production tubing above the predetermined depth is removed from the wellbore, thereby obstructing future wellbore operations.